Ferrite rods, bars, plates and tubes are primarily used in radio antennas
and chokes. They are available in materials from permeability of 20 to
10, 000.

Only rods with #61 (ui - 125), and #33 (ui = 800)
materials are standard stocking items. All other materials are custom manufactured,
readily available with lead time for delivery.

Standard Stocking Rods

Part number

Material

Permeability

Diameter
(in)

Length
(in)

AL value
mh/1000t

Ampere
turns

R61-025-400

61

125

.25

4.0

26

110

R61-037-300

61

125

.37

3.0

32

185

R61-050-400

61

125

.50

4.0

43

575

R61-050-750

61

125

.50

7.5

49

260

R33-037-400

33

800

.37

4.0

62

290

R33-050-200

33

800

.50

2.0

51

465

R33-050-400

33

800

.50

4.0

59

300

R33-050-750

33

800

.50

7.5

70

200

Other dimensions and materials are available. Please call for your other
requirements.

FERRITE RODS are available
as standard stocking items in various sizes in the #33 and #61 materials.
Ferrite rods of other materials are available with lead time. The most
common use of a ferrite rod is for antenna and choke applications.

ANTENNAS: Ferrite Rods are
widely used as loop antennas for such as broadcast-band receivers, direction-finder
receivers, etc.The #61 material rods are widely used for commercial AM
(550 KHz to 1660 KHz) radio antennas and by radio amateurs (2 MHz to 30
MHz). The #33 material rods are more suitable for very low frequency ranges
(100 KHz to 1 MHz). The table below lists the recommended frequency ranges
for a few different materials. Loop antennas have a height factor called
effective height, he (in m), which when multiplied with field
strength, F (in uV/m), provides the loop-induced voltage (in uV).

It can be seen from the equation that the highest induced voltage occurs
when the windings occupied the entire rod (when N is largest).

Initial
Permeability,
ui

Maximum
Permeability,
um

Saturation Flux
Density, Bs, at
13 Oe

Recommended
Frequency
*Range (MHz)

Material

20

--

2000 at 40 Oe

80-100

68

40

--

3000 at 20 Oe

10-80

67

125

450

2350

0.2-10

61

250

375

2200

0.05-4

64

300

3600

3900

0.001-5

83

850

3000

2750

0.01-1

43

2000

4600

1150

0.001-2

77

*Frequency ratings are for optimum Q in narrow-band tuned
circuits.

CHOKE applications: Both the #33, and the #61 rods are used extensively in choke applications. The #33 material should be selected for the 3.75 - 7.5 MHz (40-80 meters band). The #33 rods are also often used in speaker cross-over networks. The #61 material is most suitable for the 7.5-30 MHz (10-40 meters band) range. Due to the open magnetic structure of the rod
configuration, considerable current can be tolerated before it will saturate.

There are several factors that have a direct bearing on the effective permeability of a ferrite rod, which in turn will effect inductance and 'Q', as well as the AL value of the rod and its ampere-turns rating. These are: (1) Length to diameter ratio of the rod, (2) Placement of the coil on the rod, (3) Spacing between turns and, (4) Air space between the coil and the rod. In some cases, the effective permeability of the rod will be influenced more by a change in the length to diameter ration than by a change in the initial permeability of the rod. At other times, just the reverse will be true.

Greatest inductance and AL value will be obtained when the winding is
centered on the rod rather than placed at either end. The best 'Q' will
be obtained with the winding covers the entire length of the rod.

Because of all of the above various conditions it is very difficult
to provide workable AL values. However we have attempted to provide a set
of AL and NI values for various types of rods in our stick. These figures
are based on a closely wound coil of #22 wire, placed in the center of
the rod and covering nearly the entire length. Keep in mind that there
are many variables and that the inductance will vary according to winding
technique.

EFFECTIVE PERMEABILITY
Coil placements and the length of windings on the rods, bars, plates and
tubes affect the effective permeability of these devices. The corrected
permeability for variation in coil length versus rod length is:

EFFECTS ON 'Q'
The spacing between the turns has a significant effect on the 'Q', and
the inductance of the rods. The best values of 'Q' are obtained when the
coil turns are spaced one wire diameter apart, with the windings located
at the center of the rod. Litz wire provides the highest level of 'Q'.

Except for those rods (#61 & #33) listed above, the following plates,
rods, tubes and strips are non-stocking items. Non-stocking items are custom
manufactured parts with lead times. Please call for information on pricing
and delivery. Those stocking item rods can be shipped out immediately.
The materials available are: #68 (ui = 20), #67 (ui = 40), #61 (ui = 125,
#33 (ui = 800), #77 (ui = 2000), #73 (ui = 2500), #F (ui = 3000), #J (ui
= 5000), and #W (ui = 10, 000). The rods, tubes and strips can be manufactured
in lengths up to a maximum of 12 inches. The dimensional tolerances for
rods, tubes, and strips are approximately +/- 6%, and for plates are +/-
2%. All length tolerances are +/- 2%. The camber tolerance is 0.11 per
inch. (dimensional graphics and tables)

figure 1

Part numbering: Insert ( ) for material desired and insert (_ _ _) for length desired when ordering. All dimensions are in inches.